The correct Sheltie ear is beautiful. It contributes to a soft, intelligent expression and gives an alert look to the entire dog. It is set high, opening forward, semi-erect. The top third of the leather breaks forward with no inclination to turn to the sides. The ear itself is small in relation to the head; the leather strong, yet flexible, and of medium thickness.
Unfortunately for the breeder, ears can be difficult. They are influenced not only by heredity, but also by emotional stress, teething, puberty, coat loss, temperature, hormone changes, calcium assimilation, humidity, and age. And to top this off, they rarely inherit as predicted.
Some ears are perfect regardless of the environment and others are utterly hopeless. The majority of ears, however, can be helped at crucial times - especially during teething from about 10 weeks of age to nine months.
Surgical correction is undesirable and is forbidden by AKC for show dogs. It is, however, perfectly legitimate to try to improve the appearance of a dog by working on his ears.
(text from the book Sheltie Talk, by Betty Jo McKinney and Barbara Hagen Rieseberg)
There are several methods that breeders use to train the ears to "tip". A popular method is to glue the ear using Speed Sew. This is a fabric glue that can be used to glue the tip of the ear to the base of the ear by gluing hair to hair.
Another option is the moleskin method. For more information see the web page "Correcting That Ear Problem" at http://www.highledgeshelties.com/perfectears.htm.